Darstellung und Oxidation von 2-(2,5-Dihydroxy-phenyl)-ethylamin-Derivaten, II / Synthesis and Oxidation of 2-(2,5-Dihydroxyphenyl)-ethylamine Derivatives, II

Abstract

Abstract 2,5-Dihydroxyphenylethylamine derivatives 8a,b; 14; 19a,b and 25a,b,c are synthesized and oxidized to indole 9a, indolines 15 and 18a,b as well as 24a,b,c. Quantitative oxidation of hydroquinones yields the 2-(aminoethyl)quinones 30a as free base and 30d-f; 27a,b and the hydrochlorides 28a,b. Quinone 30a is reduced to indoline 29 and acetylated to 3-acylindole 32, transformed by heating to indole 23 and in acetic acid to the dimeric indole 31. 32 is synthesized unequivocally from 33 and 34. The course of the reaction is discussed and the formation of indolines is explained by cyclisation of a semiquinone precursor (43).